background image




Helicopter IFR Operations

f. The RFM also identifies other specific limita-

tions associated with IFR flight. Typically, these

limitations include, but are not limited to:

1. Minimum equipment required for IFR flight

(in some cases, for both single pilot and two pilot


2. Vmini (minimum speed − IFR).


The manufacturer may also recommend a minimum IFR

airspeed during instrument approach.

3. Vnei (never exceed speed − IFR).
4. Maximum approach angle.
5. Weight and center of gravity limits.
6. Aircraft configuration limitations (such as

aircraft door positions and external loads).

7. Aircraft system limitations (generators,

inverters, etc.).

8. System testing requirements (many avionics

and AFCS/AP/FD systems incorporate a self−test


9. Pilot action requirements (such as the pilot

must have his/her hands and feet on the controls

during certain operations, such as during instrument

approach below certain altitudes).

g. It is very important that pilots be familiar with

the IFR requirements for their particular helicopter.

Within the same make, model and series of helicopter,

variations in the installed avionics may change the

required equipment or the level of augmentation for

a particular operation.

h. During flight operations, pilots must be aware

of the mode of operation of the augmentation

systems, and the control logic and functions

employed. For example, during an ILS approach

using a particular system in the three−cue mode

(lateral, vertical and collective cues), the flight

director  collective cue responds to glideslope

deviation, while the horizontal bar of the “cross−

pointer” responds to airspeed deviations. The same

system, while flying an ILS in the two−cue mode,

provides for the horizontal bar to respond to

glideslope deviations. This concern is particularly

significant when operating using two pilots. Pilots

should have an established set of procedures and

responsibilities for the control of flight director/auto-

pilot modes for the various phases of flight. Not only

does a full understanding of the system modes

provide for a higher degree of accuracy in control of

the helicopter, it is the basis for crew identification of

a faulty system.

i. Relief from the prohibition to takeoff with any

inoperative instruments or equipment may be

provided through a Minimum Equipment List (see

14 CFR Section 91.213 and 14 CFR Section 135.179,

Inoperative Instruments and Equipment). In many

cases, a helicopter configured for single pilot IFR

may depart IFR with certain equipment inoperative,

provided a crew of two pilots is used. Pilots are

cautioned to ensure the pilot−in−command and

second−in−command meet the requirements of

14 CFR Section 61.58, Pilot−in−Command Profi-

ciency Check: Operation of Aircraft Requiring More

Than One Pilot Flight Crewmember, and 14 CFR

Section 61.55, Second−in−Command Qualifications,

or 14 CFR Part 135, Operating Requirements:

Commuter and On−Demand Operations, Subpart E,

Flight Crewmember Requirements, and Subpart G,

Crewmember Testing Requirements, as appropriate.

j. Experience has shown that modern AFCS/AP/

FD equipment installed in IFR helicopters can, in

some cases, be very complex. This complexity

requires the pilot(s) to obtain and maintain a high

level of knowledge of system operation, limitations,

failure indications and reversionary modes. In some

cases, this may only be reliably accomplished

through formal training.